According to a report in McClatchy, the
CIA secretly monitored computers used by Senate Intelligence
Committee staffers that the spy agency had provided for the review of
thousands of pages of classified documents.

The alleged monitoring occurred as the Senate Intelligence Committee prepared a 6,000 page report into the
CIA's post-9/11 torture program, details from which the agency has
fought to keep secret. The CIA responded to the investigation, which McClatchy described as a "searing indictment" of the program, with an "unprecedented action," as
Senator Mark Udall put it in a letter to President Obama. The CIA's
inspector general has launched an investigation into the matter.

"As you are aware, the CIA has
recently taken unprecedented action against the Committee in relation
to the internal CIA review, and I find these actions to be incredibly
troubling for the Committee's oversight responsibilities and for
our democracy," Udall wrote. "It is essential that the Committee
be able to do its oversight work — consistent with our
constitutional principle of the separation of powers — without
the CIA posing impediments or obstacles as it is today."

The specifics of the "unprecedented
action" weren't released or discussed in the letter, but officials told McClatchy and the New York Times that the CIA monitored the computers used by Intelligence Committee aides in a
secure room at the agency's headquarters in Langley, Va.

The New York Times reports the alleged
spying took place "after C.I.A. officials came to suspect that
congressional staff members had gained unauthorized access to agency
documents during the course of the Intelligence Committee's
years-long investigation into the detention and interrogation
program."

Sen. Dianne Feinstein, who oversees the Intelligence Committee and has strongly supported the Snowden-revealed spying operations carried by the NSA and CIA, confirmed to the Times that an investigation into the matter was underway.